Heat bacon and butter in heavy 4- to 5-quart casserole over medium heat.
When bacon begins to brown, remove with slotted spoon.
Increase heat to medium-high, add onion and cook until golden brown.
Reduce heat to low, stir in paprika and cook briefly, stirring constantly.
Add pork and toss to combine well.
Add broth, cover and simmer about 1 hour, or until pork is barely tender.
Stir in sauerkraut, reserved bacon, tomato paste and caraway seed; cover and cook 30 minutes, or until pork is tender, adding more broth if mixture seems dry.
Season to taste with salt and pepper.
Refrigerate until ready to serve.
Pass sour cream separately.
Can be prepared 3 to 4 days before serving or frozen for up to a month.